code: def sess_time(self):
      if self._sess_stop_time:
          return self._sess_stop_time - self._sess_start_time
      else:
          return time.time() - self._sess_start_time
  
imports: import asyncio
  import math
  import time
  from collections import defaultdict
  from tabulate import tabulate
label_desc: Use image node_id 3 for calling the Stat obj's underlying member method code with example usage: obj.sess_time() and returns: unknown, unknown